The 15th Gordon Research Conference on Fertilization and the Activation of Development will provide a forum for presentation and discussion of new developments and ideas in this exciting, rapidly advancing field. This meeting will be held at the Holderness School, Plymouth, New Hampshire, July 17-22, 2005. This conference has been held every 2 years since 1974. It is the only Gordon Research Conference concerned with the interaction of the male and the female gametes in the vital process of fertilization and activation of the fertilized egg to begin the process of embryo formation. It provides a venue for the interaction of biochemists, cell biologists, molecular biologists, physiologists, geneticists and biophysicists working in the field. This conference has been singularly successful in fostering collaborations among scientists with widely disparate experience and seniority from this country, Europe, Japan, Australia and Latin America. These collaborations have borne many fruitful results. There will be 9 sessions in the conference that follow the Gordon Research Conference format. 8 sessions will focus on: 1) Bioinformatic, genomic, and proteomic approaches to fertilization and development; 2) Sperm motility and chemotaxis; 3) Gamete maturation; 4) Functional membrane domains in gametes; 5) Molecular aspects of sperm-egg interaction; 6) Signal transduction in sperm; 7) Signaling events during egg activation; 8) Gene activation during early development. These sessions will include both scheduled speakers as well as selected short talks chosen from posters and/ or late breaking topics. Particular emphasis has been placed on junior scientists, including postdoctoral fellows and graduate students. In addition, we will have a keynote speaker for the Wednesday evening session.